Question

Differentiate between roasting and calcination with examples.

Answer 1

Hint: This question is asked from the chapter of metallurgy. We know that the calcination and roasting are some steps used in the process of isolation of elements from its ore.

Complete step by step answer:
We know that metals are extracted from their ores through a series of processes. Most commonly, metals are extracted from oxide ores by doing reduction or electrolysis. The process of reduction of oxide ores are very easy but that is not in the case of sulphide and carbonate ores. For the easy extraction of metals from these sulphide and carbonate ores, we need to convert the sulphide ores and carbonate ores into oxide ores. The conversion of sulphide and carbonate ores into oxide ores are done through calcination and roasting. Let us look at the process of calcination and roasting.
The process of heating the ore strongly below its melting point and thus converting the ores into oxides is called calcination. The calcination is carried out in a limited supply of air or absence of air. The example for calcination is the decomposition of calcium carbonate into calcium oxide and carbon dioxide.
\[CaC{O_3} \to CaO + C{O_2}\]

The roasting is the process of converting the sulphide ores into oxide ore by heating strongly above the melting point. This process occurs in excess of air. The roasting will result in major air pollution. The example for the roasting is zinc sulphide is converted into zinc oxide.
\[2ZnS + 3{O_2} \to 2ZnO + C{O_2}\]

Note: You should notice that the roasting and calcination is the process of converting ores into oxides by heating strongly. Please note the point that calcination is mostly used for oxidation of carbonate ores while roasting is used for oxidation of sulphide ores.